Characterisation of Fusarium oxysporum species complex associated with Fusarium wilt of sweet potato in South Africa

Abstract

Sweet potato is a popular food security crop in South Africa and has a considerable commercial value. Fusarium wilt (FW), caused by the fungal pathogen Fusarium oxysporum formae speciales (f. sp.) batatas, has been reported worldwide and is widespread in sweet potato production areas in South Africa. Preliminary molecular identification of South African isolates from diseased sweet potato plants indicated that there are other formae speciales besides F. oxysporum f. sp. batatas associated with FW. The objectives of the study were to conduct a field survey and to characterise the isolates of the Fusarium oxysporum species complex (FOSC) using phylogenetic analyses, morphological characterisation and DNA barcoding. Phylogenetic analyses revealed two other formae speciales, namely F. oxysporum f. sp. tuberosi and F. oxysporum f. sp. vanillae that were associated with FW. This study has contributed in understanding and knowledge of FOSC associated with FW of sweet potato in South Africa.